A hydrocarbon fluid such as, for example, crude oil is a complex and variable mixture of many organic molecules, but mainly, hydrocarbons ranging from low molecular weight alkanes to high molecular weight compounds such as, for example, waxes and asphaltenes. Generally, the high molecular weight paraffins are soluble under normal reservoir conditions. However, as Carnahan discloses in the October 1989 issue of J. Pet. Technol. (pages 1024-1025, 1106), the high molecular weight paraffins may precipitate in production wells and equipment if the thermodynamic equilibrium of the crude oil is disturbed, for example, by changes in pressure and temperature. Paraffin precipitation and crystal growth increases the viscosity of crude oil for transportation and forms deposits inside production tubing and transportation pipelines. Transportation can be disrupted when the paraffin buildup becomes excessive and the flow is restricted or completely stopped. Consequently, the operation has to be shut in to remove the buildup, or in some cases, abandoned.
Many procedures have been developed to control paraffin precipitation. For example, in wire .lining tubing, precipitates inside the production tubing can be mechanically cut by running a scraper. Pigging operations are used to mechanically remove deposits from transportation pipelines. Paraffin precipitation can also be prevented by either heating or insulating the production and transportation systems. Various chemical treatments, such as, for example, solvents, polymers, surfactants, and dispersants have been used to prevent paraffin deposition. Each of these procedures has its own disadvantages. For example, polymers known for wax crystal modification generally only work in low water content crude oils and are tailored to the specific crude oil.
Therefore it would be a significant contribution to the art if a process were developed in which wax deposition was controlled during the production, or transportation, or both, of crude oil.